Display device

ABSTRACT

According to one embodiment, a display device includes a first transparent substrate, a second transparent substrate, a liquid crystal layer, light-emitting elements disposed in a first direction, a third transparent substrate including a main surface and a side surface opposed to the light-emitting elements, and a transparent layer disposed on the main surface and having a lower refractive index than the third transparent substrate. The third transparent substrate is bonded to the first transparent substrate or the second transparent substrate with the transparent layer sandwiched in between. The transparent layer includes strip portions disposed in the first direction and extended along a second direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 17/351,807,filed Jun. 18, 2021, which is a continuation of application Ser. No.17/147,529, filed Jan. 13, 2021, which is a continuation of PCTApplication No. PCT/JP2019/027823, filed Jul. 12, 2019 and based uponand claiming the benefit of priority from Japanese Patent ApplicationNo. 2018-138604, filed Jul. 24, 2018, the entire contents of all ofwhich are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a display device.

BACKGROUND

Recently, various forms of display device have been proposed. Anillumination device including a light modulation layer containing a bulkand fine particles having optical anisotropy in a light modulationelement bonded to a light guide plate is disclosed. In another example,a light source device including a light conversion portion whichcontains a polymer dispersed liquid crystal layer and converts anincident light intensity is disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing one configuration example of a displaydevice DSP of the present embodiment.

FIG. 2 is a cross-sectional view showing one configuration example ofthe display panel PNL shown in FIG. 1.

FIG. 3 is an exploded perspective view showing main parts of the displaydevice DSP shown in FIG. 1.

FIG. 4 is a plan view showing one configuration example of alight-guiding element LG shown in FIG. 3.

FIG. 5 is a cross-sectional view showing one configuration example ofthe display device DSP of the present embodiment.

FIG. 6 is a cross-sectional view for explaining undesired scattering atan inclined surface.

FIG. 7 is a plan view showing one configuration example of a state wherea transparent layer 40 and a first substrate SUB1 overlap.

FIG. 8 is a plan view showing one configuration example of a state wherethe transparent layer 40 and a sealant SE overlap.

FIG. 9 is a plan view showing another configuration example of thelight-guiding element LG shown in FIG. 3.

FIG. 10 is a plan view showing another configuration example of thelight-guiding element LG shown in FIG. 3.

FIG. 11 is an enlarged plan view of strip portions 41 which are adjacentto one another.

FIG. 12 is an enlarged plan view of strip portions 41 which are adjacentto one another.

FIG. 13 is a cross-sectional view for explaining diffraction caused bythe transparent layer 40.

FIG. 14 is a cross-sectional view for explaining an evanescent wave.

FIG. 15 is a cross-sectional view showing another configuration exampleof the display device DSP of the present embodiment.

DETAILED DESCRIPTION

According to the present embodiment, there is provided a display deviceincluding: a first substrate including a first transparent substrate, ascanning line, a signal line crossing the scanning line, a switchingelement electrically connected to the scanning line and the signal line,and a pixel electrode electrically connected to the switching element; asecond substrate including a second transparent substrate, and a commonelectrode opposed to the pixel electrode; a liquid crystal layer heldbetween the first substrate and the second substrate and containing astripe-shaped polymer and liquid crystal molecules; a plurality oflight-emitting elements disposed in a first direction; a thirdtransparent substrate including a main surface, and a side surfaceopposed to the light-emitting elements; and a transparent layer disposedon the main surface and having a lower refractive index than the thirdtransparent substrate. The third transparent substrate is bonded to thefirst transparent substrate or the second transparent substrate with thetransparent layer sandwiched in between. The transparent layer includesa plurality of strip portions disposed in the first direction. The stripportions extend along a second direction orthogonal to the firstdirection.

According to the present embodiment, there is provided a display deviceincluding: a first transparent substrate including a first main surfaceand a second main surface on an opposite side to the first main surface;a second transparent substrate including a third main surface opposed tothe second main surface; a liquid crystal layer located between thesecond main surface and the third main surface and contains astripe-shaped polymer and liquid crystal molecules; a plurality oflight-emitting elements disposed in a first direction; a thirdtransparent substrate including a fourth main surface opposed to thefirst main surface, and a side surface opposed to the light-emittingelements; a transparent adhesive layer which bonds the first transparentsubstrate and the third transparent substrate together; and atransparent layer located between the first main surface and the fourthmain surface and having a lower refractive index than the thirdtransparent substrate. The transparent layer includes a plurality ofstrip portions disposed at intervals in the first direction.

The present embodiment will be described hereinafter with reference tothe accompanying drawings. The disclosure is merely an example, andproper changes in keeping with the spirit of the invention, which areeasily conceivable by a person of ordinary skill in the art, come withinthe scope of the invention as a matter of course. In addition, in somecases, in order to make the description clearer, the widths,thicknesses, shapes, and the like of the respective parts areillustrated schematically in the drawings, rather than as an accuraterepresentation of what is implemented. However, such schematicillustration is merely exemplary, and in no way restricts theinterpretation of the invention. In addition, in the specification anddrawings, constituent elements which function in the same or a similarmanner to those described in connection with preceding drawings aredenoted by the same reference numbers, and detailed explanations of themthat are considered redundant are appropriately omitted.

FIG. 1 is a plan view showing one configuration example of a displaydevice DSP of the present embodiment. A first direction X, a seconddirection Y and a third direction Z are orthogonal to one another in oneexample but may cross one another at an angle other than 90 degrees. Thefirst direction X and the second direction Y correspond to directionsparallel to the main surface of a substrate constituting the displaydevice DSP, and the third direction Z corresponds to the thicknessdirection of the display device DSP. In the present specification, adirection from a first substrate SUB1 toward a second substrate SUB2 isreferred to as an upper side (or simply above), and a direction from thesecond substrate SUB2 toward the first substrate SUB1 is referred to asa lower side (or simply below). When described as “the second memberabove the first member” and “the second member below the first member”,the second member may be in contact with the first member or apart fromthe first member. Furthermore, an observation position where the displaydevice DSP is observed is assumed to be located on a pointing end sideof an arrow indicating the third direction Z, and viewing toward an X-Yplane defined by the first direction X and the second direction Y fromthis observation position is referred to as planar view.

In the present embodiment, a liquid crystal display device employing apolymer dispersed liquid crystal will be explained as an example of thedisplay device DSP. The display device DSP includes a display panel PNL,an IC chip 1 and a wiring board 2.

The display panel PNL includes a first substrate SUB1, a secondsubstrate SUB2, a liquid crystal layer LC and a sealant SE. The firstsubstrate SUB1 and the second substrate SUB2 are formed in a flat plateshape parallel to the X-Y plane. The first substrate SUB1 and the secondsubstrate SUB2 overlap in planar view. The first substrate SUB1 and thesecond substrate SUB2 are bonded together by the sealant SE. The liquidcrystal layer LC is held between the first substrate SUB1 and the secondsubstrate SUB2 and is sealed by the sealant SE. In FIG. 1, the liquidcrystal layer LC and the sealant SE are indicated by different hatchlines.

As enlarged and schematically shown in FIG. 1, the liquid crystal layerLC includes a polymer dispersed liquid crystal containing a polymer 31and liquid crystal molecules 32. In one example, the polymer 31 is aliquid crystal polymer. The polymer 31 is formed in a stripe shapeextending along the first direction X. The liquid crystal molecules 32are dispersed in gaps of the polymer 31, and are aligned such that theirmajor axes extend along the first direction X. The polymer 31 and theliquid crystal molecule 32 each have optical anisotropy or refractiveanisotropy. The responsiveness to an electric field of the polymer 31 isless than the responsiveness to an electric field of the liquid crystalmolecule 32.

In one example, the alignment direction of the polymer 31 hardly changesregardless of the presence or absence of an electric field. On the otherhand, the alignment direction of the liquid crystal molecule 32 changesin accordance with an electric field in a state where a high voltage ofgreater than or equal to a threshold value is applied to the liquidcrystal layer LC. In a state where voltage is not applied to the liquidcrystal layer LC, the optical axis of the polymer 31 and the opticalaxis of the liquid crystal molecule 32 are parallel to each other, andlight entering the liquid crystal layer LC is transmitted almost withoutbeing scattered in the liquid crystal layer LC (transparent state). In astate where voltage is applied to the liquid crystal layer LC, theoptical axis of the polymer 31 and the optical axis of the liquidcrystal molecule 32 cross each other, and light entering the liquidcrystal layer LC is scattered in the liquid crystal layer LC (scatteringstate).

The display panel PNL includes a display portion DA which displays animage and a frame-shaped non-display portion NDA which surrounds thedisplay portion DA. The sealant SE is located in the non-display portionNDA. The display portion DA includes pixels PX arrayed in a matrix inthe first direction X and the second direction Y.

As shown enlarged in FIG. 1, each pixel PX includes a switching elementSW, a pixel electrode PE, a common electrode CE, the liquid crystallayer LC and the like. The switching element SW is composed of, forexample, a thin-film transistor (TFT) and is electrically connected to ascanning line G and a signal line S. The scanning line G is electricallyconnected to the switching elements SW in the respective pixels PXdisposed in the first direction X. The signal line S is electricallyconnected to the switching elements SW of the respective pixels PXdisposed in the second direction Y. The pixel electrode PE iselectrically connected to the switching element SW. Each pixel electrodePE is opposed to the common electrode CE and drives the liquid crystallayer LC (in particular, the liquid crystal molecules 32) by an electricfield generated between the pixel electrode PE and the common electrodeCE. A capacitance CS is formed, for example, between an electrode havingthe same potential as the common electrode CE and an electrode havingthe same potential as the pixel electrode PE.

The first substrate SUB1 has edge portions E11 and El2 which extendalong the first direction X and edge portions El3 and El4 which extendalong the second direction Y. The second substrate SUB2 has edgeportions E21 and E22 which extend along the first direction X and edgeportions E23 and E24 which extend along the second direction Y. In theexample shown in FIG. 1, the edge portions E12 and E22, the edgeportions E13 and E23, and the edge portions El4 and E24 overlap,respectively, in planar view. However, these edge portions may notoverlap. The edge portion E21 is located between the edge portion E11and the display portion DA in planar view. The first substrate SUB1 hasan extension portion Ex between the edge portion Ell and the edgeportion E21.

The IC chip 1 and the wiring board 2 are each connected to the extensionportion Ex. The IC chip 1 has, for example, a built-in display driverwhich outputs a signal necessary for image display, and the like. Thewiring board 2 is a bendable flexible printed circuit board. Note thatthe IC chip 1 may be connected to the wiring board 2. The IC chip 1 andthe wiring board 2 read a signal from the display panel PNL in somecases, but mainly function as a signal source which supplies a signal tothe display panel PNL.

FIG. 2 is a cross-sectional view showing one configuration example ofthe display panel PNL shown in FIG. 1. The first substrate SUB1 includesa transparent substrate 10, insulating films 11 and 12, a capacitanceelectrode 13, the switching element SW, the pixel electrode PE and analignment film AL1. The first substrate SUB1 further includes thescanning line G and the signal line S shown in FIG. 1. The transparentsubstrate 10 includes a main surface (lower surface) 10A and a mainsurface (upper surface) 10B on an opposite side to the main surface 10A.The switching element SW is disposed on the main surface 10B. Theinsulating film 11 covers the switching element SW. The capacitanceelectrode 13 is located between the insulating films 11 and 12. On theinsulating film 12, the pixel electrode PE is disposed for each pixelPX. The pixel electrode PE is electrically connected to the switchingelement SW via an opening OP of the capacitance electrode 13. The pixelelectrode PE overlaps the capacitance electrode 13 across the insulatingfilm 12 and forms the capacitance CS of the pixel PX. The alignment filmAL1 covers the pixel electrode PE.

The second substrate SUB2 includes a transparent substrate 20, alight-shielding layer BM, the common electrode CE and an alignment filmAL2. The transparent substrate 20 includes a main surface (lowersurface) 20A and a main surface (upper surface) 20B on an opposite sideto the main surface 20A. The main surface 20A of the transparentsubstrate 20 faces the main surface 10B of the transparent substrate 10.The light-shielding layer BM and the common electrode CE are disposed onthe main surface 20A. The light-shielding layer BM is located, forexample, directly above the switching element SW and directly above thescanning line G and the signal line S which are not shown in thedrawing. The common electrode CE is disposed over the pixels PX anddirectly covers the light-shielding layer BM. The common electrode CE iselectrically connected to the capacitance electrode 13 and has the samepotential as the capacitance electrode 13. The alignment film AL2 coversthe common electrode CE. The liquid crystal layer LC is located betweenthe main surface 10B and the main surface 20A and is in contact with thealignment films AL1 and AL2. In the first substrate SUB1, the insulatingfilms 11 and 12, the capacitance electrode 13, the switching element SW,the pixel electrode PE and the alignment film AL1 are located betweenthe main surface 10B and the liquid crystal layer LC. In the secondsubstrate SUB2, the light-shielding layer BM, the common electrode CEand the alignment film AL2 are located between the main surface 20A andthe liquid crystal layer LC.

The transparent substrates 10 and 20 are insulating substrates such asglass substrates or plastic substrates. The main surfaces 10A and 10Band the mains surfaces 20A and 20B are surfaces substantially parallelto the X-Y plane. The insulating film 11 is formed of a transparentinsulating material such as silicon oxide, silicon nitride, siliconoxynitride or acrylic resin. In one example, the insulating film 11includes an inorganic insulating film and an organic insulating film.The insulating film 12 is an inorganic insulating film formed of siliconnitride or the like. The capacitance electrode 13, the pixel electrodePE and the common electrode CE are transparent electrodes formed of atransparent conductive material such as indium tin oxide (ITO) or indiumzinc oxide (IZO). The light-shielding layer BM is, for example, aconductive layer having a lower resistance than the common electrode CE.In one example, the light-shielding layer BM is formed of anontransparent metal material such as molybdenum, aluminum, tungsten,titanium or silver. The alignment films AL1 and AL2 are horizontalalignment films having an alignment restriction force substantiallyparallel to the X-Y plane. In one example, the alignment films AL1 andAL2 are provided with alignment treatment along the first direction X.Note that the alignment treatment may be rubbing treatment orphoto-alignment treatment.

FIG. 3 is an exploded perspective view showing main parts of the displaydevice DSP shown in FIG. 1. The display device DSP includes alight-guiding element LG and a plurality of light-emitting elements LDin addition to the display panel PNL. The light-guiding element LG, thefirst substrate SUB1 and the second substrate SUB2 are disposed in thisorder along the third direction Z. The light-emitting elements LD aredisposed at intervals in the first direction X. The light-emittingelements LD are connected to a wiring board F. The light-emittingelement LD is, for example, a light-emitting diode. Although notdescribed in detail, the light-emitting element LD includes a redlight-emitting portion, a green light-emitting portion and a bluelight-emitting portion. Light emitted from the light-emitting element LDtravels along the direction of an arrow indicating the second directionY.

The light-guiding element LG includes a transparent substrate 30 and atransparent layer 40.

The transparent substrate 30 is an insulating substrate such as a glasssubstrate or a plastic substrate and has a refractive index nl. In oneexample, the transparent substrate 30 is not composed of a plurality ofsubstrates bonded together but is a single substrate. The transparentsubstrate 30 includes a main surface (lower surface) 30A, a main surface(upper surface) 30B on an opposite side to the main surface 30A, and aside surface 30C. The main surfaces 30A and 30B are surfacessubstantially parallel to the X-Y plane. The main surface 30B faces themain surface 10A of the transparent substrate 10. The side surface 30Cis a surface substantially parallel to an X-Z plane defined by the firstdirection X and the third direction Z. The side surface 30C faces thelight-emitting elements LD. As will be described later, the transparentsubstrate 30 is bonded to the transparent substrate 10 with thetransparent layer 40 sandwiched in between. The side surface 30C islocated directly below the edge portion Ell of the first substrate SUB1in the example shown in FIG. 3, but may be located directly below theextension portion Ex or more outward than the edge portion Ell.

The transparent layer 40 is disposed on the main surface 30B. Thetransparent layer 40 has a refractive index n2 which is less than therefractive index nl of the transparent substrate 30. The transparentlayer 40 includes a plurality of strip portions 41 disposed at intervalsin the first direction X. Each strip portion 41 extends along the seconddirection Y. The main surface 30B is exposed between the strip portions41 which are adjacent to each other. The detailed shape of thetransparent layer 40 will be described later.

The transparent substrate 30 is formed of, for example, glass, anorganic material such as polymethylmethacrylate (PMMA) or polycarbonate(PC). The transparent layer 40 is formed of, for example, an organicmaterial such as siloxane-based resin or fluorine-based resin. Therefractive index nl of the transparent substrate 30 is about 1.5, andthe refractive index n2 of the transparent layer 40 is about 1.0 to 1.4.In the example shown in FIG. 3, the main surface 30A of the transparentsubstrate 30 is in contact with air. However, another transparent layerhaving an equal refractive index to the transparent layer 40 may bedisposed over the entire surface of the main surface 30A.

FIG. 4 is a plan view showing one configuration example of thelight-guiding element LG shown in FIG. 3. The transparent layer 40includes the strip portions 41 and a frame portion 42 surrounding thestrip portions 41. The strip portions 41 and the frame portion 42 areintegrally formed.

The strip portion 41 includes a first end portion 411 on a side opposedto the light-emitting element LD, a second end portion 412 on anopposite side to the first end portion 411, a first edge 413, and asecond edge 414. The first end portion 411 and the second end portion412 have a first width W1 and a second width W2, respectively. Note thata width in the specification corresponds to a length along the firstdirection X. The first width W1 is greater than the width W2. In oneexample, the first width W1 is less than a width WL of onelight-emitting element LD, and one light-emitting element LD is disposedover a plurality of strip portions 41 disposed in the first direction X.In addition, the first width W1 is less than or equal to a width WP ofone pixel electrode PE (or the pitch of the pixel electrodes PE disposedin the first direction X). The first width W1 may be equal to the secondwidth W2 in the strip portion 41, and the strip portion 41 may be formedwith a uniform width.

The first edge 413 and the second edge 414 extend in differentdirections from the first direction X and the second direction Y betweenthe first end portion 411 and the second end portion 412. For example, adirection crossing at an acute angle clockwise with respect to thesecond direction Y is defined as a direction D1, and a directioncrossing at an acute angle counterclockwise with respect to the seconddirection Y is defined as a direction D2. Note that an angle el formedby the second direction Y and the direction D1 and an angle θ2 formed bythe second direction Y and the direction D2 are the same. However, thisis in no way restrictive, and the angle formed by the second direction Yand the direction D1 and the angle formed by the second direction Y andthe direction D2 may be different from each other. The first edge 413extends along the direction D1, and the second edge 414 extends alongthe direction D2. Here, the first edge 413 and the second edge 414 bothextend straight but may be formed curved. The first width W1 and thesecond width W2 correspond to the gap between the first edge 413 and thesecond edge 414. The strip portion 41 of such a shape has a width whichgradually decreases at a constant rate or an arbitrary rate from thefirst end portion 411 to the second end portion 412.

When focusing on two adjacent strip portions 41, the gap between thefirst end portions 411 and the gap between the second end portions 412have a third width W3 and a fourth width W4, respectively. The thirdwidth W3 is less than the first width W1, the fourth width W4 is lessthan the second width W2, and the third width W3 is less than the fourthwidth W4. In one example, the second width W2 is about 2/3 the firstwidth W1, the first width W1 is about 9 times the third width W3, thesecond width W2 is about 1.5 the fourth width W4, and the fourth widthW4 is about 4 times the third width W3. The pitch of the adjacent stripportions 41 should preferably be less than or equal to twice the widthWP of the pixel electrode PE (or the pitch of the pixel electrodes PEdisposed in the first direction X).

The pixel electrode PE overlaps two adjacent strip portions 41 in planarview. The pixel electrode PE overlaps the main surface 30B of thetransparent substrate 30 between the strip portions 41. Attention ispaid to a pixel electrode PE1 closest to the light-emitting element LDand a pixel electrode PE2 farthest from the light-emitting element LD inthe display portion DA. An area in which the pixel electrode PE1overlaps the strip portions 41 is greater than an area in which thepixel electrode PE2 overlaps the strip portions 41. In addition, an areain which the pixel electrode PE1 overlaps the main surface 30B is lessthan an area in which the pixel electrode PE2 overlaps the main surface30B. As will be described later, a region overlapping the strip portion41 corresponds to a region in which light from the light-emittingelement LD hardly enters, and a region overlapping the main surface 30Bcorresponds to a region in which light from the light-emitting elementLD can enter.

When the display panel PNL shown in FIG. 3 and the light-guiding elementLG are superimposed, in planar view, the strip portions 41 overlap thedisplay portion DA, and the frame portion 42 overlaps the non-displayportion NDA. The frame portion 42 includes a first portion 421 and asecond portion 422 which extend along the first direction X, and a thirdportion 423 and a fourth portion 424 which extend along the seconddirection Y. The first portion 421 is located between the light-emittingelements LD and the display portion DA. The first portion 421 isconnected to the first end portions 411 of the respective strip portions41. The second end portions 412 of the respective strip portions 41 areconnected to the second portion 422 in the example shown in FIG. 4 butmay be apart from the second portion 422. The strip portion 41 does notinclude an edge parallel to the first direction X in the display portionDA, and only the first edge 413 and the second edge 414 which areinclined with respect to the first direction X and the second directionY overlap the display portion DA.

FIG. 5 is a cross-sectional view showing one configuration example ofthe display device DSP of the present embodiment. Note that, regardingthe display panel PNL, only main parts are illustrated. Theconfiguration example shown in FIG. 5 corresponds to an example wherethe transparent substrate 30 of the light-guiding element LG is bondedto the transparent substrate 10 of the first substrate SUB1 by atransparent adhesive layer AD. The transparent layer 40 including thestrip portion 41 is in contact with the main surface 30B. While thetransparent adhesive layer AD is in contact with substantially theentire surface of the main surface 10A, the transparent adhesive layerAD covers the transparent layer 40 and is in contact with the mainsurface 30B in a region in which the transparent layer 40 is missing.The main surface 20B of the transparent substrate 20 is in contact withair, but another transparent substrate similar to the transparentsubstrate 30 may be bonded to the main surface 20B.

The refractive indexes of the transparent substrates 10 and 20 and thetransparent adhesive layer AD are equal to the refractive index n1 ofthe transparent substrate 30 and are greater than the refractive indexn2 of the transparent layer 40. Being “equal” here is not limited to acase where a refractive index difference is zero but includes a casewhere a refractive index difference is less than or equal to 0.03.

The transparent substrate 10 has a thickness T1, the transparentsubstrate 20 has a thickness T2, and the transparent substrate 30 has athickness T3. Note that a thickness in the specification corresponds toa length along the third direction Z. In the illustrated example, thethickness T1 and the thickness T2 are equal, and the thickness T3 isgreater than the thicknesses T1 and T2. Note that the thickness T3 maybe equal to the thicknesses T1 and T2. In one example, the thickness T3is 200 μm to 2000 μm. A thickness T4 of the transparent layer 40 will bedescribed later. A thickness T5 of the transparent adhesive layer AD is4 μm to 4000 μm.

Next, the emitted light from the light-emitting element LD will beexplained with reference to FIG. 5.

The light-emitting element LD emits light L1 toward the side surface30C. Since an air layer is present between the light-emitting element LDand the side surface 30C, the light L1 emitted from the light-emittingelement LD is refracted at the side surface 30C and enters thetransparent substrate 30. Light traveling toward the transparent layer40 from the transparent substrate 30 of the light L1 entering thetransparent substrate 30 is reflected at the interface between thetransparent substrate 30 and the transparent layer 40. In addition,light traveling toward the main surface 30A of the light L1 entering thetransparent substrate 30 is reflected at the interface between thetransparent substrate 30 and an air layer. As described above, close tothe side surface 30C (or in a region in which the transparent layer 40is present), the light L1 travels inside the transparent substrate 30while being repeatedly reflected. Light traveling toward a region inwhich the transparent layer 40 is not present, that is, a region inwhich the transparent substrate 30 and the transparent adhesive layer ADare in contact with each other of the traveling light L1 is transmittedthrough the transparent substrate 30 and is transmitted through thetransparent substrate 10 via the transparent adhesive layer AD. That is,while the entry to the display panel PNL of the light L1 from thelight-emitting element LD is suppressed in a region close to thelight-emitting element LD, the entry to the display panel PNL of thelight L1 is promoted in a region away from the light-emitting elementLD. Note that not all the entry to the display panel PNL of the light L1is suppressed in the region close to the light-emitting element LD, butthe light L1 enters the display panel PNL through the gap between theadjacent strip portions 41 as shown in FIG. 4. The light L1 entering thedisplay panel PNL is transmitted through the pixel in the transparentstate and is scattered in the pixel in the scattering state. The displaydevice DSP can be observed from a main surface 30A side and can also beobserved from a main surface 40B side. In addition, the display deviceDSP is a so-called transparent display, and the background of thedisplay device DSP can be observed via the display device DSP regardlessof whether the display device DSP is observed from the main surface 30Aside or the main surface 40B side.

Meanwhile, the emitted light rays from the light-emitting elements LDdisposed at intervals generally travel while spreading, respectively,but close to the light-emitting elements LD, the emitted light rays fromthe adjacent light-emitting elements LD are not sufficiently mixedtogether in some cases. Therefore, in the display device DSP using suchlight as illumination light, when the display portion DA is planarlyviewed, stripe-like non-uniformity caused by a luminance difference arevisually perceived in the region close to the light-emitting elements LDin some cases. The luminance difference of the illumination light issmaller as the position is farther from the light-emitting elements LD.However, if the distance between the display portion AD and thelight-emitting elements LD is increased, the frame width of the displaydevice DSP is increased, accordingly.

According to the present embodiment, in the region in which thetransparent layer 40 is present, the light L1 entering from the sidesurface 30C is guided while being totally reflected inside thetransparent substrate 30, and therefore the entry of the light L1 to thedisplay device PNL is suppressed. On the other hand, in the region inwhich the transparent layer 40 is not present, the entry of the light L1to the display panel PNL is promoted.

In the display portion DA, the illumination light amount of the light L1entering the pixel electrode PE1 close to the light-emitting element LDand the illumination light amount of the light L1 entering the pixelelectrode PE2 away from the light-emitting element LD are compared. Thelight L1 from the light-emitting element LD attenuates as it travelsaway from the light-emitting element LD. The luminance of the light L1in the region close to the light-emitting element LD is referred to thefirst luminance, and the luminance of the light L1 in the region awayfrom the light-emitting element LD is referred to as the secondluminance. The second luminance is less than the first luminance. Theoverlapping area of the pixel electrode PE1 and the transparent layer 40is greater than the overlapping area of the pixel electrode PE2 and thetransparent layer 40. Therefore, the area of a region in which the lightL1 can enter the pixel electrode PE1 is less than the area of a regionin which the light L1 can enter the pixel electrode PE2. On the otherhand, the first luminance of the light L1 entering the pixel electrodePE1 is greater than the second luminance of the light L1 entering thepixel electrode PE2. Therefore, the illumination light amounts in thepixel electrode PE1 and the pixel electrodes PE2 can be equalized.

In addition, in the display portion DA, the overlapping area of each ofthe pixel electrodes PE disposed in the second direction Y and thetransparent layer 40 is optimized in accordance with a decrease in theluminance along the second direction Y of the light L1. Therefore, theillumination light amount per pixel electrode PE can be made uniformover substantially the entire region of the display portion DA.Accordingly, degradation of display quality caused by illumination lightnon-uniformity can be suppressed.

FIG. 6 is a cross-sectional view for explaining undesired scattering atan inclined surface. The cross section in the Y-Z plane shown in FIG. 6corresponds to an example where the transparent layer 40 has an inclinedsurface 40S extending along the first direction X. The inclined surface40S is inclined toward the light-emitting element LD with respect to anormal N of the main surface 30B. Alternatively, the inclined surface40S is a surface crossing at an acute angle counterclockwise withrespect to the normal N. In a case where the light L1 from thelight-emitting element LD enters the transparent layer 40, undesiredscattering occurs at the inclined surface 40S and causes degradation ofdisplay quality.

According to the present embodiment, as explained with reference to FIG.4, the transparent layer 40 does not include an edge extending along thefirst direction X in the display portion DA and does not include aninclined surface extending along the first direction X. Therefore,undesired scattering in the transparent layer 40 can be suppressed.

In the configuration example shown in FIGS. 1 to 6, the transparentsubstrate 10 corresponds to the first transparent substrate, the mainsurface 10A corresponds to the first main surface, the main surface 10Bcorresponds to the second main surface, the transparent substrate 20corresponds to the second transparent substrate, the main surface 20Acorresponds to the third main surface, the transparent substrate 30corresponds to the third transparent substrate, and the main surface 30Bcorresponds to the fourth main surface.

FIG. 7 is a plan view showing one configuration example of a state wherethe transparent layer 40 and the first substrate SUB1 are superimposed.Note that the frame portion 42 of the transparent layer 40 isillustrated but illustration of the strip portions 41 is omitted here.

The first substrate SUB1 includes a plurality of scanning lines G, aplurality of signal lines S and a power line P in the display portionDA. The scanning lines G extend along the first direction X and aredisposed at intervals in the second direction Y. The signal lines Sextend along the second direction Y and are disposed at intervals in thefirst direction X. The scanning lines G and the signal lines S are drawnto the non-display portion NDA. For example, the odd-numbered scanninglines G are drawn between the edge portion E13 and the display portionDA, and the even-numbered scanning lines G are drawn between the edgeportion E14 and the display portion DA.

The power line P is a wiring line for supplying, for example, a commonvoltage (Vcom) and is electrically connected to the capacitanceelectrode 13 shown in FIG. 2. In addition, the power line P is connectedto power terminals PT in corner portions of the first substrate SUB1.The power terminals PT are electrically connected to the commonelectrode CE of the second substrate SUB2 via a conductive materialwhich is not shown in the drawing. The power line P and the powerterminals PT are located in the non-display portion NDA, and althoughnot described in detail, the power terminals PT are located outside thesealant SE shown in FIG. 1. The power line P may be located inside thesealant SE or overlap the sealant SE.

The scanning lines G, the signal lines S and the power line P areelectrically connected to the IC chip 1 or the wiring board 2 shown inFIG. 1 between the edge portion E11 and the display portion DA.

In planar view, the third portion 423 and the fourth portion 424 of theframe portion 42 of the transparent layer 40 overlap the scanning linesG located in the non-display portion NDA. In addition, the first portion421 overlaps the scanning lines G and the signal lines S in thenon-display portion NDA. Furthermore, the frame portion 42 overlaps thepower line P and the power terminals PT.

According to this configuration example, the entry of light from thelight-emitting elements LD to various wiring lines located in thenon-display portion NDA can be suppressed, and degradation of displayquality caused by absorption in various wiring lines or undesiredscattering in various wiring lines can be suppressed.

FIG. 8 is a plan view showing one configuration example of a state wherethe transparent layer 40 and the sealant SE are superimposed. Note thatthe frame portion 42 of the transparent layer 40 is illustrated butillustration of the strip portions 41 is omitted. In planar view, theframe portion 42 of the transparent layer 40 overlaps the sealant SE.

According to this configuration example, the entry of light from thelight-emitting elements LD to the sealant SE located in the non-displayportion NDA can be suppressed, and degradation of display quality causedby undesired scattering in the sealant SE can be suppressed.

FIG. 9 is a plan view showing another configuration example of thelight-guiding element LG shown in FIG. 3. The configuration exampleshown in FIG. 9 is different from the configuration example shown inFIG. 4 in that the first edge 413 and the second edge 414 of the stripportion 41 is formed curved. A width W10 of the strip portion 41gradually decreases from the first end portion 411 toward the second endportion 412. In the example shown in FIG. 9, the width W10 changes moregreatly on a side close to the first end portion 411 than it does on aside close to the second end portion 412.

Also in this configuration example, similar effects to those of theconfiguration example shown in FIG. 4 can be obtained.

FIG. 10 is a plan view showing another configuration example of thelight-guiding element LG shown in FIG. 3. The configuration exampleshown in FIG. 10 is different from the configuration example shown inFIG. 9 in that the width W10 of the strip portion 41 changes moregreatly on the side close to the second end portion 412 than it does onthe side close to the first end portion 411.

Also in this configuration example, similar effects to those of theconfiguration example shown in FIG. 4 can be obtained.

FIG. 11 is an enlarged plan view of the strip portions 41 which areadjacent to one another. A connection portion C of the strip portion 41and the first portion 421 of the frame portion 42 is formed in a V shapeby connecting the first edge 413 and the second edge 414 of the adjacentstrip portions 41. In this configuration example, the first portion 421does not include the inclined surface 40S shown in FIG. 6 between theadjacent strip portions 41. Therefore, undesired scattering in the firstportion 421 can be suppressed. In addition, even when the first portion421 and the display portion DA approach, degradation of display qualitycaused by scattering can be suppressed.

FIG. 12 is an enlarged plan view of the strip portions 41 which areadjacent to one another. The configuration example shown in FIG. 12 isdifferent from the configuration example shown in FIG. 11 in that theconnection portion C is formed in a U shape. Also in this configurationexample, similar effects to those of the configuration example shown inFIG. 11 can be obtained.

FIG. 13 is a cross-sectional view for explaining diffraction caused bythe transparent layer 40. As described above, the transparent layer 40has a lower refractive index than the transparent substrate 30 and thetransparent adhesive layer AD. Therefore, of the light transmittedthrough the transparent substrate 30, light L11 transmitted through thetransparent layer 40 and light L12 transmitted thorough the transparentadhesive layer AD without being transmitted through the transparentlayer 40 have different phases from each other. The phase differencebetween the light L11 and the light L12 increases as the thickness T4 ofthe transparent layer 40 increases. The transmitted light of thelight-guiding element LG is diffracted by the phrase difference. If thephrase difference is large, a diffraction image is visually perceived,and display quality is degraded.

According to the examination by the inventor, it is confirmed that thevisibility of the diffraction image can be suppressed when the thicknessT4 is less than or equal to the maximum wavelength of the lighttransmitted through the light-guiding element LG. Therefore, thethickness T4 should preferably be less than or equal to 800 nm.Accordingly, degradation of display quality caused by the diffractionimage can be suppressed.

FIG. 14 is a cross-sectional view for explaining an evanescent wave. Apart of light traveling from the transparent substrate 30 toward thetransparent layer 40 enters the transparent layer 40. The light waveentering the transparent layer 40 is called an evanescent wave. As shownin (A) of FIG. 14, if the thickness T4 of the transparent layer 40 issufficiently greater than a penetration length L20 to the transparentlayer 40 of the evanescent wave, the light directed to the transparentlayer 40 is totally reflected. As shown in (B) of FIG. 14, if thethickness T4 of the transparent layer 40 is less than the penetrationlength L20, a part of the evanescent wave is transmitted through thetransparent layer 40 and is lost. Consequently, the luminance of thelight propagating through the transparent substrate 30 is reduced.

The penetration length L20 varies according to an incident angle θll atthe interface between the transparent substrate 30 and the transparentlayer 40. The inventor sets the lower limit of the thickness T4 to 250nm based on the penetration length L20 with respect to the incidentangle θll, the distribution of the incident angle θll assumed in thelight-guiding element LG of the present embodiment, the luminancedistribution with respect to the divergent angle of emitted light fromthe light-emitting element LD, and the like.

Based on the result of the above-described examination, the thickness T4should preferably be greater than or equal to 250 nm but less than orequal to 800 nm, and should more preferably be greater than or equal to400 nm but less than or equal to 550 nm.

FIG. 15 is a cross-sectional view showing another configuration exampleof the display device DSP of the present embodiment. Note that,regarding the display panel PNL, only main parts are illustrated. Theconfiguration example shown in FIG. 15 corresponds to an example wherethe transparent substrate 30 of the light-guiding element LG is bondedto the transparent substrate 20 of the second substrate SUB2 by thetransparent adhesive layer AD. The transparent layer 40 including thestrip portion 41 is in contact with the main surface 30A. While thetransparent adhesive layer AD is in contact with substantially theentire surface of the main surface 20B, the transparent adhesive layerAD covers the transparent layer 40 and is in contact with the mainsurface 30A in a region in which the transparent layer 40 is missing. Inthe example shown in FIG. 15, the main surface 30B of the transparentsubstrate 30 is in contact with air. However, another transparent layerhaving an equal refractive index to the transparent layer 40 may bedisposed on the entire surface of the main surface 30B. Theconfiguration of the display panel PNL is as described above. The mainsurface 10A of the transparent substrate 10 is in contact with air, butanother transparent substrate similar to the transparent substrate 30may be bonded to the main surface 10A.

Also in this configuration example, similar effects to those of theconfiguration example shown in FIG. 5 can be obtained.

In the configuration example shown in FIG. 15, the transparent substrate20 corresponds to the first transparent substrate, the main surface 20Bcorresponds to the first main surface, the main surface 20A correspondsto the second main surface, the transparent substrate 10 corresponds tothe second transparent substrate, the main surface 10B corresponds tothe third main surface, the transparent substrate 30 corresponds to thethird transparent substrate, and the main surface 30A corresponds to thefourth main surface.

As described above, according to the present embodiment, a displaydevice which can suppress degradation of display quality can beprovided.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A display device comprising: a first transparentsubstrate; a first electrode on the first transparent substrate; asecond transparent substrate facing the first transparent substrate; asecond electrode on the second transparent substrate; a liquid crystallayer held between the first transparent substrate and the secondtransparent substrate and containing stripe-shaped polymers extending ina first direction and liquid crystal molecules; a plurality oflight-emitting elements arranged in the first direction; a thirdtransparent substrate comprising a main surface facing the secondtransparent substrate and a side surface facing the light-emittingelements; a first transparent layer disposed between the main surface ofthe third transparent substrate and the second transparent substrate;and a second transparent layer disposed between the first transparentlayer and the second transparent substrate, wherein the firsttransparent layer has a lower refractive index than the thirdtransparent substrate and the second transparent substrate, the firsttransparent layer comprises a plurality of strip portions arranged inthe first direction, and each of the strip portions is disposed from afirst end portion of the main surface on the side surface to a secondend portion of the main surface on the opposite side along a seconddirection intersecting the first direction.
 2. The display device ofclaim 1, wherein the first transparent layer has a lower refractiveindex than the second transparent layer, and a first width of each ofthe strip portions on the first end portion is greater than a secondwidth of each of the strip portions on the second end portion.
 3. Thedisplay device of claim 2, wherein a third width of a gap between thestrip portions adjacent to each other on the first end portions is lessthan the first width, a fourth width of a gap between the strip portionsadjacent to each other on the second end portions is less than thesecond width, and the third width is less than the fourth width.
 4. Thedisplay device of claim 1, wherein the first electrode and the secondelectrode overlap the strip portions in a plan view.
 5. The displaydevice of claim 1, further comprising a display portion which displaysan image and a non-display portion which surrounds the display portion,wherein the first transparent layer further comprises a frame portionsurrounding the strip portions, and the strip portions overlap thedisplay portion and the frame portion overlaps the non-display portionin a plan view.
 6. The display device of claim 5, further comprising asealant which bonds the first transparent substrate and the secondtransparent substrate together and seals the liquid crystal layer,wherein the sealant is located in the non-display portion, and the frameportion overlaps the sealant in a plan view.